The Swede had forged a nine-stroke lead earlier in the round but stumbled to three bogeys in the final five holes as the conditions worsened at East Lake, finishing at 11-under-par 199 -- four strokes ahead of Dustin Johnson, who carded a 3-under 67 to move into second place at 7-under.
Stenson has a chance to take both The Tour Championship and the FedExCup Playoffs with a victory -- he is currently second to Tiger Woods on FedEx points list.
Steve Stricker moved into sole possession of third place at 5-under with a third-round 2-under 68.
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